Circuit Description
When the ignition switch turns ON, the Transmission Control Module (TCM) performs a 3-second OD/OFF indicator bulb check. The TCM performs the bulb check by grounding the OD/OFF indicator control circuit. The OD switch button grounds the OD/OFF signal circuit to the TCM when the OD switch button releases. The above condition causes the TCM to ground the OD/OFF indicator control circuit. Grounding the OD/OFF indicator control circuit turns on the OD/OFF indicator lamp located in the instrument panel gauge cluster. The OD/OFF indicator informs the driver that the transmission will not shift into overdrive (4th gear). The TCM dims the OD/OFF indicator lamp by adding additional internal resistance to the OD/OFF indicator control output circuit when both of the following conditions occur:
| • | The OD/OFF indicator remains on. |
| • | The parking lamps/headlamps remain on. |
Dimming the OD/OFF indicator lamp reduces excessive glare to the driver at night. The following conditions occur after the OD switch button is pressed:
- The depressed OD switch button removes a path to ground to the OD/OFF signal circuit.
- The TCM turns off the OD/OFF indicator lamp.
- The TCM adds overdrive (4th gear) to the shift schedule.
Diagnostic Aids
Inspect for the following conditions:
| • | An open OD/OFF indicator lamp bulb filament |
| • | An open IG COIL fuse |
| • | A faulty OD switch (always open) |
| • | A reduced ground (G200) |
| • | An open circuit between the TCM and the instrument panel gauge cluster |
| • | A damaged instrument panel gauge cluster printed circuit |
| • | A faulty TCM |
The following conditions may cause an intermittent condition:
| • | A reduced connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Before replacing components, inspect the inline harness connector terminals for the following conditions:
| • | Reduced connections |
| • | Backed out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Reduced terminal-to-wire connections |
Repeat the OBD System Check after making repairs in order to ensure that the system functions normally.
Refer to Wiring Repairs in Wiring Systems when repairing any wiring.
Test Description
The numbers below refer to the step numbers on this diagnostic table.
-
The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. The scan tool creates an electronic copy of the data taken when the fault occurred. The information then stores in the scan tool for later reference.
-
This step verifies that the TCM performs the bulb check.
-
This step tests the integrity of the indicator control circuit.
-
This step inspects for an open bulb filament.
-
This step tests the power source to the instrument panel gauge cluster.
-
This step tests for an open in the indicator control circuit.
-
This step verifies if the TCM responds by turning on the OD/OFF indicator when grounding the OD/OFF signal circuit.
-
This step tests for a reduced ground (G200) to the OD switch.
-
This step tests for a faulty OD switch.
-
This step tests if the condition relates to a poor connection and is not due to a faulty TCM.
-
This step tests for proper operation of the OD/OFF indicator.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Transmission On-Board Diagnostic (OBD) System Check performed? | -- | |||
Did the OD/OFF indicator lamp turn on for at least 3 seconds? | -- | |||
Does the OD/OFF indicator lamp turn on? | -- | |||
Is the bulb filament open? | -- | |||
Does the test lamp turn on? | -- | |||
Use J 39200 in order to measure the resistance between the instrument panel gauge cluster harness connector terminal 13 and the TCM harness connector terminal 20. Is the resistance less than the specified value? | 2 ohms | |||
Does the OD/OFF indicator lamp remain on after the 3-second bulb check? | -- | |||
Does the test lamp turn on? | -- | |||
Use J 39200 in order to measure the resistance across the OD switch terminals. Is the resistance less than the specified value with the switch released? | 2 ohms (∞ with the switch pressed) | |||
Inspect the TCM connector for reduced terminal contact. Replace the TCM if terminal contact is OK. Is the procedure complete? | -- | -- | ||
11 | Replace the OD/OFF indicator bulb. Is the replacement complete? | -- | -- | |
12 | Repair the open or the high resistance in the BLK/WHT wire between the instrument panel gauge cluster and the IG COIL fuse. Is the repair complete? | -- | -- | |
13 | Inspect the instrument panel gauge cluster printed circuit for cracks or opens. Replace the instrument panel gauge cluster as necessary. Is the procedure complete? | -- | -- | |
14 | Repair the open or the high resistance in the WHT/BLK wire between the instrument panel gauge cluster and the TCM. Is the repair complete? | -- | -- | |
15 | Repair the open or the high resistance in the BLK wire between the OD switch harness connector terminal 1 and G200. Is the repair complete? | -- | -- | |
16 | Replace the OD switch. Refer to O/D Cut Switch Replacement . Is the procedure complete? | -- | -- | |
17 | A malfunction does not exist at this time. Refer to Diagnostic Aids for additional information. Is the action complete? | -- | -- | |
Does the OD/OFF indicator lamp turn on for approximately 3 seconds? (The indicator will remain ON with the OD switch released). | -- | System OK |
